Life is not always as it seems, and this is particularly true in the world of film and television. Whilst we’re all used to the computerised visual effects used in modern films, we are probably not as aware of the level of special effects used in the film’s soundtrack.
Special effects has two categories, mechanial & natural.Natural sounds,The natural sounds....
Can be directly recorded from the location or same situation created by the crews.
The rest is mechanical,tht can created by the 'Archives' of sound effects[pre-recorded]
with the help of an hard disk media like computers...